Technical Field
The present disclosure relates to the manufacture of integrated circuits (ICs) from semiconductor wafers. More specifically, the present disclosure relates to methodologies for dispatching semiconductor wafers to various tools for manufacture, while accounting for the absence of historical manufacturing data for some of the available tools.
Related Art
Fabrication foundries (“fabs”) may manufacture integrated circuits (ICs) using photolithographic processes. Photolithography is an optical printing and fabrication process by which patterns on a photolithographic mask (i.e., photomask) are imaged and defined onto a photosensitive layer coating of a substrate. To manufacture an IC, photomasks are created using a specification, including an IC layout, as a template. The photomasks contain the various geometries of the IC layout. The various geometries contained on the photomasks correspond to the various base physical IC elements that make up functional circuit components such as transistors, interconnect wiring, via pads, as well as other elements that are not functional circuit elements but are used to facilitate, enhance, or track various manufacturing processes. Through sequential use of the various photomasks corresponding to a given IC in an IC fabrication process, a large number of material layers of various shapes and thicknesses with different conductive and insulating properties may be built up to form the overall IC and the circuits therein.
The manufacture of an IC may be carried out on a bulk semiconductor wafer, with a group of bulk semiconductor wafers being known as a “lot.” A single manufacturing process may employ deposition tools, etching tools, heat-transmitting devices (e.g., flash lamps, lasers, and/or hot plates), and/or other tools, each with a significant number of adjustable settings. Conventional manufacturing processes may rely upon historical data for a product, tool, operation, etc., to improve the tool's reliability and/or manufacturing quality. Such conventional processes may calibrate new tools by manufacturing a “test product,” e.g., intentionally sending wafers to a new tools to calibrate and select settings for the future manufacture of a product.
In light of the significant expense of installing new devices and the ever-increasing demand for IC products, the amount of time and resources needed to send ahead a subset of wafers to initialize the process is disadvantageous to a manufacturer. Some manufacturing lines may include “non-threaded controllers” configured to import historical data associated with other similar tools to reduce the need to use send-ahead wafers. However, a device for dispatching wafers to a tool in the manufacturing line may be unable to determine whether a sufficient amount of data is available to perform an operation on a wafer with a new tool. This technical obstacle has been shown to reduce the usefulness of non-threaded controllers.